Early hikers, park officials and Park geologists find Pinon trees in the area of Hetch Hetchy Valley in northern Yosemite and it was documented in early reports. Part of the this story was published in the Yosemite Nature Notes in January 1937. The story was about how a Sierra Club party discovered a Single-leaf or Pinon Pine in Yosemite National Park's Hetch Hetchy Valley. Then as more people traveled into the location they discovered more Pinon trees. This tree is found mainly on the eastern side of the Sierra Nevada and the nut of the tree, or pinenut, is a food staple of the Paiute Native people.

In the article published by Yosemite Nature Notes it discusses finding Pinon trees on the California western slope of the Sierra Nevada around Hetch Hetchy Valley.

http://www.yosemite.ca.us/library/yosemite_nature_notes/16/16-1.pdf

Here is excerpts from the story:

"In 1909, Mr. H. W. Gleason, with the Sierra Club party, discovered the first-known occurrence of the Single-leaf or Pinon Pine (Pinus monophylia, Torrey or Fremont) in Yosemite National Park. Jepson in his "Trees of California" issued December 15, 1909, says, "On the west slope of the Sierra Nevada it occurs in a few circumscribed localities, in Piute Canyon, near Pate Valley (Grand Canyon of the Tuolumne River), Kings River, along the west wall of the Kern Canyon, and southward into the lower Kern country." Harvey M. Hall recorded in "A Yosemite Flora," 1932, that the specimen found by Mr. Gleason was at about 5500 feet altitude in the Piute Creek Gorge. This single tree has been noted several times since by park officers. It is supposed to have been accidentally planted by Paiute Indians enroute from Mono Lake country to Pate Valley, a favorite summer camp.
During the late summer of 1935, Junior Forester Elliott Sawyer found a second lone specimen near the Rancheria Trail on the lower western slope of Rancheria Mountain. This find was recorded by Park Forester Emil Ernst in Yosemite Nature Notes for February, 1936. This tree is also on a possible route of the Paiutes entering Hetch Hetchy Valley. Now a third locality is established in the Park.
On September 14, 1936, while on a field trip with Mr. F. E. Matthes, Senior Geologist of the U.S. Geological Survey, from base camp in Tiltill Valley, I discovered a small Single-leaf Pine tree at 5800 feet altitude, 150 yards south of Tiltill Valley Trail at the point where the up-trail from Hetch Hetchy reaches top of the ridge and makes a slight dip. We were once aware of the presence of a number of trees of this species so made a survey, finding there were between 100 and 200, varying in altitude from 5800 to 6100 feet, spread over an area of some two acres."

An orchard of Pinon trees where found at that location around Hetch Hetchy. They were old and young and of different heights, some being very large. The trees were found on a series of broad, granite shelves which had a marvelous view-point over looking the Hetch Hetchy Reservoir. One of the biggest Pinon trees found in 1936 had a trunk diameter of 28 inches.

The article goes on:

"Where these trees planted by the Indians? Mr. Matthes and I noted a ducked trail out across these natural shelves to "Pinon Point" (which they named after the trees) and on up the ridge. We followed these markers EASTERLY around a high dome, and were led into the upper end of Tiltill Valley. I consulted Mr. Gabriel Sovulewski for many years Supervisor of Road and Trail construction in Yosemite, and he said he had tentatively laid out this route following an old Indian trail, but had later abandoned it for the more direct, present Tiltill Valley Trail location.

Tabuce (Maggie "Taboose" Howard), an old Paiute resident of Yosemite, told me that as a little girl she had gone several times from Mono Lake to camp for the summer with her family in Hetch Hetchy. She said they first went to Bridgeport, and her description of the route seemed to indicate they entered Tiltill Valley, where there are many mortar holes in granite, indicating villages, and then on to Hetch Hetchy, evidently by this old trail. She said children ate pine nuts as they walked along and "maybe lots of times drop'em." So perhaps a Paiute child several HUNDREDS YEARS AGO started this "orchard" of Single-leaf Pines. It would take TWO or THREE HUNDRED YEARS for one of these slow-growing pines to reach a diameter of 28 inches." (See Photo 1 in Gallery of Taboose and a 1937 photo of a Pinon tree around Hetch Hetchy)

So if you are ever hiking around Hetch Hetchy and run into the Single-Leaf Pinon trees remember they were once left there hundreds of years ago by Paiutes who camped in Hetch Hetchy Valley.